CN103329617A - Compatible with trailing edge dimmers with dimmer high impedance prediction - Google Patents

Abstract

An electronic system (100) including a controller (402) for providing compatibility between an electronic light source (410) and a trailing edge dimmer (404). The controller can predict an estimated occurrence of a trailing edge of the phase cut AC voltage and can accelerate a transition of the phase cut voltage from the trailing edge to a predetermined voltage threshold. The controller predicts an estimated occurrence of a trailing edge of the phase cut AC voltage based on actual observations of one or more previous cycles of the phase cut AC voltage.

Description

Compatible with trailing edge dimmers with dimmer high impedance prediction

Cross References to Related Applications

This application claims the benefit under 35 U.S.C. §119(e) and 37 C.F.R. §1.78 of U.S. Provisional Patent Application No. 61/414,291, filed November 16, 2010, which is hereby incorporated by reference in its entirety. This application also claims the benefit of U.S. Provisional Patent Application No. 13/298,002, filed November 16, 2010, the entire contents of which are hereby incorporated by reference under 35 U.S.C. §119(e) and 37 C.F.R. §1.78 of the United States .

technical field

The present invention relates generally to the field of electronics, and more particularly to methods and systems for making trailing edge dimmers compatible with high impedance prediction.

Background technique

The development and deployment of energy-efficient technologies remains a priority for many institutions, including many companies and countries. One area of interest is the replacement of incandescent lamps with more energy-efficient lamps, such as lamps based on electronic light sources. For this description, the electronic light sources are light emitting diodes (LEDs) and compact fluorescent lamps (CFLs). The development of lamps based on electronic light sources does not pose many challenges. One of the challenges is to develop lamps based on electronic light sources that are compatible with existing infrastructure. The following discussion focuses on LED-based lighting systems, but is also applicable to CFL-based lighting systems and combined LED and CFL-based lighting systems.

Many electronic systems include circuits such as switching power converters connected to dimmers. The interface circuit supplies power to the load according to the dimming level set by the dimmer. For example, in a lighting system, a dimmer provides an input signal to the lighting system. The input signal represents a dimming level that causes the lighting system to adjust the power supplied to the lamps, thus increasing or decreasing the brightness of the lamps according to the dimming level. There are many different types of dimmers. Typically, dimmers generate digital or analog coded dimming signals indicative of desired dimming levels. A trailing edge dimmer phase cuts the trailing edge of an alternating current ("AC") supply voltage.

FIG. 1 shows a lighting system 100 including a trailing edge phase-cut dimmer 102 . FIG. 2 shows an exemplary trailing edge phase cut voltage graph 200 and dimmer control signal 201 associated with lighting system 100 . Referring to FIGS. 1 and 2 , the lighting system 100 receives an AC supply voltage V _IN from a supply voltage 104 . The supply voltage V _IN represented by voltage waveform 202 is, for example, a nominal 60Hz/110V line voltage in the United States of America or a nominal 50Hz/220V line voltage in Europe. The trailing edge dimmer 102 phase cuts trailing edges, such as trailing edges 202 and 204 , of each half cycle of the supply voltage V _IN . Since each half cycle of the supply voltage V _IN is 180 degrees of the supply voltage V _IN , the trailing edge dimmer 102 cuts the supply voltage V _IN with an angular phase greater than 0 degrees and less than 180 degrees. The phase cut input voltage _{VΦ_IN} to the lighting system 100 represents a dimming level that causes the lighting system 100 to adjust the power supplied to the lamp 106, thus increasing or decreasing the brightness of the lamp 106 according to the dimming level. Lamp 106 is an incandescent lamp and can generally be modeled as resistor 108 .

The dimmer 102 includes a timing controller 110 that generates a dimmer control signal DCS for controlling the duty cycle of a switch 112 . The duty cycle of the switch 112 is the pulse width, eg for each cycle of the dimmer control signal DCS, which is the dimmer control signal period, eg time t ₃ -t ₀ divided by time t ₁ -t ₀ . The timing controller 110 translates the desired dimming level into a duty cycle of the switch 112 . For lower dimming levels, ie higher brightness of the lamp 106, the duty cycle of the dimmer control signal DCS is decreased, and for higher dimming levels, the duty cycle of the dimmer control signal DCS is increased. During pulses of dimmer control signal DCS (eg, pulse 206 and pulse 208 ), switch 112 conducts (ie, opens), and dimmer 102 enters a low impedance state. In the low impedance state of the dimmer 102, the resistance of the switch 112 is less than or equal to, for example, 10 ohms. During the low impedance state of switch 112 , phase cut input voltage V _{Φ — in} follows input supply voltage V _IN , and dimmer 102 delivers dimmer current i _DIM to lamp 106 .

When the timing controller 110 ends the pulse of the dimmer control signal 206 , the dimmer control signal 206 closes the switch 112 , which puts the dimmer 102 into a high impedance state, ie, off. In the high impedance state of the dimmer 102, the resistance of the switch 112 is greater than, for example, 1k ohms. The dimmer 102 includes a capacitor 114 that charges the supply voltage VIN during each pulse of the dimmer control signal DCS. Capacitor 114 remains connected across switch 112 during the high impedance and low impedance states of dimmer 102 . When switch 112 is closed and dimmer 112 enters a high impedance state, the voltage V _C across capacitor 114 decays, for example, between times _t1 and _t2 and between _t4 and _t5 . The rate of decay is a function of the capacitance C of capacitor 114 and the dimmer current i _DIM flowing through resistor R of lamp 108 . Equation [1] expresses the relationship between the capacitance C of the capacitor 114, the dimmer current i _DIM and the decay rate dV _{Φ_IN} /dt of the phase-cut input voltage V _{Φ_IN} :

i _DIM =C·dV _{Φ_IN} /dt [1]

The resistance value R of the lamp 106 is relatively low and allows a sufficiently high value of the dimmer current i _DIM to allow the phase-cut input voltage V _{Φ_IN} to decay to a zero crossing before the next pulse of the dimmer control signal DCS, e.g. times t ₂ and t ₅ .

A trailing edge dimmer, such as trailing edge dimmer 102, has several advantageous properties. For example, the trailing edge dimmer 102 has no sudden voltage increase when the dimmer 102 starts to conduct (eg, at times _t0 and _t3 ), and has a decrease in attenuation when the dimmer 102 enters a high impedance state. Therefore, the harmonic frequencies are lower and dimmer 102 generates less electromagnetic interference.

As mentioned above, electronic light sources are more energy efficient than incandescent lamps which output a comparable amount of light. Accordingly, electronic light sources are retrofitted into existing infrastructure including trailing edge dimmers, such as trailing edge dimmer 102 . Electronic light sources have lower power requirements, therefore, less dimmer current i _DIM is delivered to the electronic light source. Therefore, according to the formula [1], the smaller the dimmer current i _DIM is, the smaller the decay rate dV _{Φ_IN} /dt is. If the decay rate dV _{Φ_IN} /dt is too low, the phase-cut input voltage V _{Φ_IN} will not reach the zero-crossing point before the next cycle of the supply voltage V _IN starts. Failure to reach the zero crossing will cause some trailing edge dimmers to fail.

FIG. 3 shows a lighting system 300 including trailing edge dimmer 102 and LED 302 . The dimmer 102 has the aforementioned functions and provides the phase cut input voltage V _{Φ_IN} and the dimmer current to the full bridge diode rectifier 304 . The rectifier 304 provides the phase-cut rectified voltage V _{Φ — R} to the power converter 306 . The power converter 306 converts the phase-cut rectified voltage V _{Φ_R} and the rectified input current i _R into approximately constant voltage V _OUT and output current i _OUT , respectively. The output current i _OUT is adjusted according to the dimming level indicated by the phase angle of the phase cut input voltage V _{Φ_IN} and is approximately constant for any given dimming level.

Controller 308 includes a current controller 310 that controls the delivery of current i _R to power converter 306 and regulates the power delivered to LED 302 . LEDs require substantially less power to provide the equivalent light output of incandescent lamps. For example, LED 302 uses 4W of power to provide the equivalent light output of a 60W incandescent lamp. The output voltage V _OUT is typically boosted by the power converter 306 to, for example, 400V. Since the power P supplied to the LED 302 is approximately P=V _OUT ·i _OUT , the maximum current i _R delivered to the power converter 306 is typically only 50mA, which is less than the approximately 545mA maximum current drawn by a 60W lamp from a 110V supply input voltage VIN . Therefore, according to the formula [1], the decay time dV _{Φ — IN} /dt of the lighting system 300 increases. The controller 308 includes a comparator 312 for detecting trailing edges, such as trailing edges 314 and 316 , of the phase-cut rectified voltage V _{Φ_R} .

The detection of the trailing edge of the phase-cut rectified voltage V _{Φ_R} is not a simple task. The trailing edges of the rectified input voltage V _{ΦR_IN} at times _t1 and _t4 are typically noisy and may include other distortions. To detect the trailing edge, the controller 308 uses the comparator 312 to detect the trailing edge at a more stable portion of the phase-cut rectified voltage _{VΦ_R} . The comparator 312 receives the phase cut rectified voltage V _{Φ_R} or a scaled version of the phase cut rectified voltage V _{Φ_R} at the inverting input of the comparator 312 . The comparator 312 compares the phase cut rectified voltage V _{Φ_R} with a fixed trailing edge detection voltage threshold (eg +20V), and generates a trailing edge detection signal TE_DETECT. Before detecting the trailing edge of the phase-cut rectified voltage _{VΦ_R} , the trailing edge pulse detection signal TE_DETECT is logic 0, and changes to logic 1 after detecting the trailing edge. Once the trailing edge detection signal TE_DETECT indicates that a trailing edge is detected, the current controller 310 increases the current i _DIM flowing through the dimmer 102 to increase the decay rate dVΦ_IN/dt, thus increasing the phase-cut rectified voltage V _{Φ_R} at, for example, time t ₂ and a decay rate of _t4 . Increasing the decay rate at times _t2 and _t5 helps to ensure that the phase-cut rectified voltage V _{Φ_R} reaches the zero-crossing point before the next cycle of the phase-cut rectified voltage V _{Φ_R} begins. The trailing edge detection threshold is set low enough to avoid premature detection of a trailing edge. However, since the decay rate dV _{Φ_IN} /dt is large for electron sources, the low value of the trailing edge detection threshold also means that, for large phase angles, the detection may not occur until the zero crossing of the phase-cut rectified voltage V _{Φ_R} to the trailing edge. Increasing the value of the trailing edge detection threshold can result in an unnecessary amount of current being delivered from the voltage supply 104 .

Improved compatibility of trailing edge dimmers is desired.

Contents of the invention

In one embodiment of the invention, the apparatus includes a controller for providing compatibility between the lamp and the trailing edge dimmer. The controller is capable of predicting the estimated occurrence of the high impedance state of the trailing edge dimmer. A high-impedance state occurs when a trailing-edge dimmer begins phase-cutting an alternating current (AC) voltage signal. The controller is further capable of operating in a high current mode based on the estimated predicted occurrence of the high impedance state of the trailing edge dimmer. The controller is also capable of operating in a low impedance mode after the AC voltage signal reaches a low voltage threshold.

In another embodiment of the present invention, a method for providing compatibility between a lamp and a trailing edge dimmer includes predicting an estimated occurrence of a high impedance state of the trailing edge dimmer. A high-impedance state occurs when a trailing-edge dimmer begins phase-cutting an alternating current (AC) voltage signal. The method further includes operating at least a controller of the power converter in a high current mode based on the estimated occurrence of the predicted high impedance state of the trailing edge dimmer. The method also includes operating the controller in a low impedance mode after the AC voltage signal reaches a low voltage threshold.

In another embodiment of the invention, the apparatus includes a controller capable of predicting the estimated occurrence of the high impedance state of the trailing edge dimmer. The high impedance state occurs when the trailing edge dimmer begins to phase cut an alternating current (AC) voltage signal that phase cuts the AC voltage. The controller is further capable of accelerating the transition of the AC voltage from the trailing edge to the predetermined voltage threshold.

In yet another embodiment of the invention, the method includes predicting the estimated occurrence of the high impedance state of the trailing edge dimmer. The high impedance state occurs when the trailing edge dimmer begins to phase cut an alternating current (AC) voltage signal that phase cuts the AC voltage. The method further includes accelerating the transition of the AC voltage from the trailing edge to the predetermined voltage threshold.

Description of drawings

The present invention may be better understood, and its numerous objects, features and advantages made apparent to those skilled in the art by referencing the accompanying drawings. Throughout the several drawings, the same reference numerals indicate similar or analogous elements.

Figure 1 (labeled prior art) shows a lighting system comprising a trailing edge dimmer.

FIG. 2 (labeled Prior Art) shows dimmer control signals and voltage waveforms associated with the trailing edge dimmer of FIG. 1 .

Figure 3 (labeled prior art) shows a lighting system comprising a trailing edge dimmer 102 and LEDs.

Figure 4 shows a lighting system comprising a controller for providing compatibility between a trailing edge dimmer and an electronic light source.

FIG. 5 shows exemplary voltage and current waveforms during operation of the lighting system of FIG. 4 .

6 illustrates an exemplary trailing edge compatibility operational flowchart representing one embodiment for providing compatibility between the trailing edge dimmer of FIG. 4 and electronic light sources.

FIG. 7 shows a lighting system representing one embodiment of the lighting system of FIG. 4 .

Figure 8 shows the zero crossing and active period detectors.

Figure 9 shows the current control module.

Detailed ways

In at least one embodiment, the electronic system includes a controller, and the controller provides compatibility between the electronic light source and the trailing edge dimmer. In at least one embodiment, the controller can predict the estimated occurrence of the trailing edge of the phase-cut AC voltage and can accelerate the transition of the phase-cut AC voltage from the trailing edge to a predetermined voltage threshold. The term "forecast" and its derivatives "predict" and "prophet" mean to state or indicate in advance. Thus, in at least one embodiment, predicting the estimated occurrence of the trailing edge of the phase-cut AC voltage pre-declares or indicates that the estimated occurrence of the trailing edge of the phase-cut AC voltage occurs. In at least one embodiment, the controller predicts the estimated occurrence of the trailing edge of the phase-cut AC voltage based on actual observations of one or more previous cycles of the phase-cut AC voltage.

In at least one embodiment, in order to provide compatibility between the trailing edge dimmer and the electronic light source, the controller predicts the estimated occurrence of the high impedance state of the trailing edge dimmer. The trailing edge of the phase cut AC voltage begins when the trailing edge dimmer enters the high impedance state. Therefore, a high impedance state occurs when a trailing edge dimmer begins to phase cut an alternating current (AC) voltage signal. Based on the prediction that the estimated high impedance state of the trailing edge dimmer occurs, the controller can and is configured to further operate in the high current mode to increase the delivery of current from the trailing edge dimmer. Operating in the high current mode increases the decay rate of the phase cut AC voltage and, in at least one embodiment, ensures that the phase cut AC voltage reaches the low voltage threshold before starting another cycle. Once the phase cut AC voltage reaches the low voltage threshold, the controller can and is configured to operate in a low impedance mode to maintain the phase cut AC voltage at or below the low voltage threshold.

FIG. 4 shows a lighting system 400 including a controller 402 that provides compatibility between a trailing edge dimmer 404 and a light source 410 . Trailing edge dimmer 404 may be any trailing edge dimmer, such as trailing edge dimmer 102 that phase cuts the trailing edge of input supply voltage V _IN from supply voltage 104 . The full-bridge diode rectifier 408 rectifies the phase-cut input voltage V _{Φ_IN} to generate a phase-cut rectified voltage V _{Φ_R} . The power converter 406 receives the phase-cut rectified voltage V _{Φ_R} and the rectified current i _R to generate an output voltage V _OUT and an output current i _OUT . The output voltage V _OUT and the output current i _OUT provide power for the light source 410 . In at least one embodiment, light source 410 is an electronic light source comprising one or more LEDs, one or more CFLs, or a combination of one or more LEDs and one or more CFLs. Power converter 406 may be any type of power converter and may include, for example, a boost converter, a buck converter, a boost converter, or a Cúk converter.

FIG. 5 shows exemplary voltage and current waveforms 500 of the lighting system 400 during operation. FIG. 6 illustrates an exemplary trailing edge compatibility operational flowchart 600 representing one embodiment of providing compatibility between trailing edge dimmers 404 and light sources 410 . Referring to FIG. 4 , FIG. 5 and FIG. 6 , each period of the phase-cut rectified voltage V _{Φ_R} has an effective period from the first zero-crossing point to the second zero-crossing point. The waveform 500 shows a series of valid periods T _A (n) _˜TA (nN) of the phase-cut rectified voltage V _{Φ_R} , where n is an integer index and N is an integer greater than or equal to one. "Active period T _A (nX)" refers to a portion where the phase-cut AC voltage is not approximately equal to 0 for "X" ranging from 0 to N. In at least one embodiment, the controller 402 predicts the estimated active period of the nth cycle of the phase-cut rectified voltage V _{Φ_R} , which crosses from the first zero-crossing T _A (n) _EST at time t _ZC (n) ₁ to the active The next approximate zero crossing t _ZC (n) ₂ of the period T _A (n) _EST . T _A (n) _EST represents the predicted estimated value of the effective period T _A (n) of the current nth cycle.

In at least one embodiment, the controller 402 includes a trailing edge dimmer high-impedance state predictor 412 that utilizes the actual measured effective period T _A (n-1) to N previous cycles of the phase-cut rectified voltage V _{Φ_R} to T _A (nN), predicting the estimated effective period T _A (n) _EST of the nth period, where N is an integer greater than or equal to 1. The trailing edge dimmer high impedance state predictor 412 detects the phase cut rectified voltage V _{Φ — R} at node 414 . Each effective period T _A (nX) is equal to the time between the first zero-crossing point t _ZC (nX) ₁ and the second zero-crossing point t _ZC (nX) ₂ of the (nX)th cycle of the rectified input voltage V _{ΦR_IN} . Therefore, in at least one embodiment, in operation 602, the trailing edge dimmer high impedance state detector ₄₁₂ detects the approximate zero-crossing points t _ZC (nX) ₁ and t _ZC ( nX) ₂ to determine the effective period T _A (nX) of the phase-cut rectified voltage V _{Φ_R} for X ranging from 1 to N.

In operation 603 , the trailing edge dimmer high impedance state predictor 412 predicts the estimated active period T _A (n) _EST of the nth cycle of the phase-cut rectified voltage V _{Φ_R} . The specific algorithm for predicting the estimated effective period T _A (n) _EST is selected according to the design. In at least one embodiment, the trailing edge dimmer high impedance state predictor 412 assumes that the estimated active period T _A (n) _EST is equal to the previous actual measured active period T _A (n−1). In at least one embodiment, the trailing edge dimmer high impedance state predictor 412 employs an algorithm reflecting the time trend of the active period T _A (nX) of the previous N cycles of the phase-cut rectified voltage V _{Φ_R} . For example, in at least one embodiment, N is equal to 2, and the trailing edge dimmer high impedance state predictor 412 uses equation [2] to determine the trend of the duration of the active period to predict the estimated nth active period T _A (n) _EST :

T _A (n) _EST =T _A (nl)+T _A (nl)-T _A (n-2)=2 T _A (nl)-T _A (n-2) [2]

In the formula [2], T _A (n) _EST represents the predicted effective period of the nth period, T _A (n-1) represents the approximate actual period of the previous (n-1)th period, and T _A (n -2) represents the approximate actual measurement period of the previous (n-2)th cycle. As discussed in detail in connection with FIG. 8 , the trailing edge dimmer high impedance state predictor 412 detects the approximate actual zero crossing of each active period of the phase-cut rectified voltage V _{Φ — R.} In at least one embodiment, the trailing edge dimmer high impedance state predictor 412 determines approximately the actual active period T _A (n) using the detection of the actual zero crossing. When estimating the actual period of the next cycle of the phase-cut rectified voltage V _{Φ_R} , the determined approximate actual period T _A (n) becomes the approximate actual period T _A (nl) used in equation [2], and in When estimating the actual period of the period after the next period of the phase-cut rectified voltage _{VΦ_R} , it becomes the approximate actual period T _A (n-2) used in Equation [2].

In at least one embodiment, the trailing edge dimmer high impedance state predictor 412 separates odd and even periods of the phase-cut rectified voltage V _{Φ_R} due to better correlation between odd and even periods. When separating the odd and even periods, the trailing edge dimmer high impedance state predictor 412 uses equation [3] to determine the trend of the duration of the even active period to predict the estimated nth active period T _A (n) _EST :

T _A (n) _EST =T _A (n-2)+T _A (n-2)-T _A (n-4)=2 T _A (n-2)-T _A (n-4) [3 ],

When separating the even and odd periods, the trailing edge dimmer high impedance state predictor 412 uses equation [4] to determine the trend of the duration of the even active period to predict the estimated n+1th active period T _A (n ) _EST :

T _A (n+l) _EST =T _A (nl)+T _A (nl)-T _A (n-3)=2·T _A (nl)-T _A (n-3) [4]

In operation 604 , the trailing edge dimmer high impedance state predictor 412 detects the first approximate zero crossing t _ZC (n) ₁ of the current nth cycle of the phase cut rectified voltage V _{Φ_R} . Based on the known first zero crossing time t _ZC (n) ₁ of cycle n and the predicted estimated effective period T _A (n) _EST , the trailing edge dimmer high impedance state predictor 412 predicts when the second crossing will occur. Zero point t _ZC (n) ₂ .

In operation 606, the trailing edge dimmer high-impedance state predictor 412 is based on the detection of the first approximate zero-crossing point t _ZC (n) ₁ of the current n-th cycle based on the duration of n previous cycles of the phase-cut rectified voltage V _{Φ_R} , predicting the estimation of the high impedance state of the trailing edge dimmer 404 to occur. In at least one embodiment, by assuming that the occurrence of the high impedance state of the trailing edge dimmer 404 is equal to the predicted second zero crossing t _ZC (n) ₂ of the nth cycle minus the nth cycle of the phase-cut rectified voltage V _{Φ_R} The estimated decay time T _DC (n) of the trailing edge 502 , the trailing edge dimmer high impedance state predictor 412 determines that the predicted estimated occurrence of the high impedance state of the nth cycle of the trailing edge dimmer 404 occurs.

The method of obtaining the estimated decay time T _DC (n) is a design choice. In at least one embodiment, trailing edge dimmer high impedance state predictor 412 is based on the worst case value of a capacitor (eg, capacitor 114 ) ( FIG. 1 ) of trailing edge dimmer 404 and the current controlled by current control module 416 . For flow i _DIM , a pre-stored estimated decay time T _DC (n), for example 180 μs, is used. In other embodiments, the trailing edge dimmer high impedance state predictor 412 employs any one of several algorithms to determine the estimated decay time T _DC (n) of the phase-cut rectified voltage V _{Φ — R} . For example, in at least one embodiment, the estimated decay time is stored in a look-up table (not shown) for various capacitance values of the trailing edge dimmer 404 and the phase-cut angle of the phase-cut rectified voltage V _{Φ_R} , and is determined by The trailing edge high impedance state predictor 412 accesses. In at least one embodiment, the capacitance value of trailing edge dimmer 404 is stored in optional memory 417 of trailing edge dimmer high impedance state predictor 412 . In at least one embodiment, the trailing edge dimmer high impedance state predictor 412 measures or determines the decay time T _DC (nl) of the previous (nl)th cycle of the phase-cut rectified voltage V _{Φ_R} , and adopts the previous (nl)th cycle ) cycle decay time T _DC (n-1) is used as the decay time T _DC (n) of the current n-th cycle of the phase-cut rectified voltage V _{Φ_R} . In at least one embodiment, the decay time of the light source 410 at a particular phase cut angle is determined experimentally in a laboratory setting using an actual dimmer and an actual light source (eg, LED and/or CFL). Next, the decay time of the phase-cut rectified voltage V _{Φ_R} is stored in the optional non-volatile memory 417 via the terminal 419 of the controller 402 and used by the trailing edge dimmer high impedance state predictor 412 to predict the trailing edge dimmer. Estimation of the high impedance state of optical device 404 occurs.

In at least one embodiment, operation 606 takes into account that as the dimming level decreases, the cycle-to-cycle phase angle of the phase-cut rectified voltage V _{Φ_R} decreases. To compensate for the potential reduction in phase angle, the trailing edge dimmer high impedance state predictor 412 subtracts the dynamic dimming level compensation time T _DDLC from the second zero crossing time t _ZC (n) ₂ to obtain the dimmer at time The prediction of the high impedance state of t _HR (n) occurs. _The dynamic dimming _level compensation time T _DDLC value is a _matter of design choice and, in at least one _embodiment , represents the maximum possible Variety. In at least one embodiment, the dynamic dimming level compensation time t _DDLC is 120 μs. Thus, in at least one embodiment, the predicted occurrence t _HR (n) of the high impedance state of the dimmer is equal to t _ZC (n) ₂ −(T _DC −T _DDLC ). In at least one embodiment, the dynamic dimming level compensation time t _DDLC is a percentage of the decay time T _DC (n), such as 50-75%. The trailing edge dimmer high impedance state predictor 412 provides a HRSTATE_PREDICTION signal to the current control module 416 to indicate the predicted occurrence t _HR (n) of the high impedance state of the dimmer.

In operation 608 , the trailing edge dimmer high impedance state predictor 412 increases the dimming value delivered to the power converter 406 through the trailing edge dimmer 404 when the prediction of the high impedance state of the dimmer occurs t _HR (n). Optical current amount i _DIM . The increase of the dimmer current i _DIM reduces the decay time T _DC , thus accelerating the transition of the trailing edge of the n-th cycle of the phase-cut rectified voltage V _{Φ_R} to the predetermined threshold voltage. In at least one embodiment, the predetermined voltage threshold is in the range of 0 to 65V. In an exemplary description of current i _R as a rectified version of dimmer current i _DIM , current i _R follows the phase-cut rectified voltage V _{Φ_R} until the predicted occurrence of the dimmer high impedance state t _HR (n). At the predicted occurrence t _HR (n) of the dimmer high impedance state, the current control module 416 increases the current i _R delivered by the trailing edge dimmer 404 to the power converter 406 to the trailing edge accelerator current compared to normal operation Value i _{R_ACCEL} .

The specific value of the trailing accelerator current value i _{R_ACCEL} is a matter of design choice. Increasing the trailing accelerator current value i _{R_ACCEL} reduces the decay time T _DC and increases the dimming range of the lighting system 400 . Decreasing the trailing accelerator current value i _{R_ACCEL} increases the decay time T _DC and reduces the dimming range of the lighting system 400 . The dimming range of the lighting system 400 is increased due to the increased phase cut angle range relative to the dimming level, while still ensuring that the phase cut rectified voltage _{VΦ_R} reaches a zero crossing before the next zero crossing. However, increasing the trailing edge accelerator current value i _{R — ACCEL} also potentially increases the amount of power dissipated by the power converter 406 . Moreover, increasing the trailing accelerator current value i _{R_ACCEL} results in higher current ratings and more expensive components for the power converter 406 .

In at least one embodiment, the current control module 416 dynamically adjusts the trailing accelerator current value i _{R_ACCEL} to ensure operation in discontinuous current mode (DCM) while minimizing power dissipation. In at least one embodiment, the controller 402 can switch between a DCM mode of operation, a continuous conduction mode (CCM), and/or a critical conduction mode (CRM) to allow the current control module 416 to flexibly select the trailing edge accelerator current value i _{R_ACCEL} . DCM is when the phase-cut rectified voltage V _{Φ_R} reaches the second zero-cross point t _ZC (nX) ₂ before the first zero _- cross point t _ZC (n-X+l) ₁ of the next cycle of the phase-cut rectified voltage V Φ_R. CCM is when the phase-cut rectified voltage V _{Φ_R} does not reach the second zero-cross point t _ZC (nX) ₂ before the first zero-cross point t _ZC (n-X+l) ₁ of the next cycle of the phase-cut rectified voltage V _{Φ_R} . CRM is when the second zero-crossing point t _ZC (nX) ₂ is the same as the first zero-crossing point t _ZC (n-X+l) ₁ of the next cycle of the phase-cut rectified voltage V _{Φ_R} .

In at least one embodiment, the trailing edge accelerator current value i _{R_ACCEL} is 100-500% higher than the normal operating current peak value i _R . In at least one embodiment, the normal operating current peak value is approximately 100 mA and the trailing edge accelerator current value i _{R_ACCEL} is approximately 500 mA. In at least one embodiment, the power converter 406 includes one or more optional power dissipation circuits 418 that deliver the additional current i _R and dissipate power associated with the additional current i _R . Exemplary power dissipation circuits are described in: (i) "Controlled PowerDissipation in a Switch Path in a Lighting System," filed Nov. 4, 2011, inventors John L. Melanson and Eric J .King's U.S. Patent Application No. 13/289,845; (ii) U.S. Patent entitled "Controlled Power Dissipation in a Lighting System," filed Nov. 4, 2011, inventors John L. Melanson and Eric J. King Application Serial No. 13/289.931; and (iii) U.S. Patent entitled "Controlled PowerDissipation in a Link Path in a Lighting System," filed November 4, 2011, inventors John L. Melanson and Eric J. King Application No. 13/289,967.

In at least one embodiment, because the supply voltage 104 is capable of supplying a current value well in excess of the trailing accelerator current value i _{R_ACCEL} , if the dimming level is increased and thus the phase angle of the phase-cut rectified voltage V _{Φ_R} increases rather than decreases, the trailing edge The accelerator current value i _{R_ACCEL} does not distort the waveform of the phase-cut rectified voltage V _{Φ_R} .

In at least one embodiment, at each second zero crossing t _ZC (nX) ₂ , the current control module 416 controls the current i _R delivered through the dimmer 404 such that the power converter 406 enters a low impedance state. In at least one embodiment, the current flow in the low impedance state is referred to as the stick current, which is generally described in the following patent document: "Dimmer Output Emulation" filed on August 7, 2010 ", the inventors of which are: U.S. Patent Application Serial No. 12/858,164, filed August 24, 2011, by John L. Melanson (referred to herein as "Melanson I") and entitled "Multi-Mode Dimmer Interfacing Including AttachState Control", the inventors are: US Patent Application No. 13/217,174 to Eric J. King and John L. Melanson, the entire contents of the above two patent applications are hereby incorporated by reference.

The specific implementation of trailing edge dimmer high impedance state predictor 412 may be a matter of design choice. The trailing edge dimmer high impedance state predictor 412 may be implemented using analog circuitry, digital circuitry, or both, and may be implemented using discrete components. In at least one embodiment, the controller 402 is an integrated circuit, and the trailing edge dimmer high impedance state predictor 412 and the current control module 416 are implemented as part of the integrated circuit. In at least one embodiment, the controller 402 includes a processor (not shown) and a memory (not shown) that stores and executes code implementing one or more of the exemplary back-edge compatible operational flowchart 600. implementation.

FIG. 7 shows a lighting system 700 as one embodiment of the lighting system 400 . The lighting system 700 includes a controller 702 that includes a trailing edge dimmer high impedance state predictor 412 . The trailing edge dimmer high impedance state predictor 412 generates the HRSTATE_PREDICT1ON signal and provides the HRSTATE_PREDICT1ON signal to the current control module 704 to indicate the predicted occurrence t _HR (n) of the dimmer's high impedance state, as previously described with reference to the lighting system 400 describe. The current control module 704 controls the boost switching power converter 706 using the same current and voltage profiles discussed with reference to the lighting system 400 and described in the exemplary voltage and current waveforms 500 ( FIG. 5 ). Switching power converter 706 includes boost switch 707, and current control module 704 controls power factor correction, and regulates the link voltage V _LINK across link capacitor 708 as described in the following patent document: filed December 31, 2007 , U.S. Patent Application No. 11/967,269, entitled "Power Control System Using a Nonlinear Delta-Sigma Modulator With Nonlinear Power Conversion Process Modeling," by John L. Melanson (referred to herein as "Melanson I") as inventor; filed in 2007 U.S. Patent Application Serial No. 11/967,275, entitled "Programmable Power Control System," to John L. Melanson (referred to herein as "Melanson II"), filed December 31; filed June 30, 2009 Submission entitled "Cascode Configured Switching Using at Least One Low Breakdown Voltage Internal, Integrated Circuit Switch to Control At Least One High Breakdown Voltage External Switch", inventor John L. Melanson (herein referred to as "Melanson III") US Patent Application Serial No. 12/495,457; and U.S. Patent Application Serial No. 12/174,404, filed June 30, 2011, entitled "Constant Current Controller With Selectable Gain," inventors John L. Melanson, Rahul Singh, and Siddharth Maru No., the entirety of which is incorporated herein by reference.

The switching power converter includes a capacitor 710 that filters high frequency components of the rectified voltage V _{ΦR_IN} . Gate bias voltage V _G biases the gate of switch 707 . The specific value of gate bias voltage V _G is a matter of design choice and depends on operating parameters of switch 707 , for example. In at least one embodiment, the gate bias voltage _VG is +12V. To control the operation of the switching power converter 706 , the controller 702 generates a control signal CS ₁ that controls the conduction of a field effect transistor (FET) switch 707 . The control signal CS ₁ is a pulse width modulated signal. Each pulse of control signal CS ₁ causes switch 707 to open (ie, conduct) and inductor current i _R to increase to charge inductor 712 . Diode 714 prevents current flow from link capacitor 708 to switch 707 . When the pulse ends, the inductor 712 reverses the voltage polarity (often referred to as "retrace"), and during the retrace phase, the inductor current _iR decreases. Inductor current i _R boosts the link voltage across link capacitor 708 through diode 714 . The switching power converter 706 is a boost converter, therefore, the link voltage V _LINK is greater than the phase-cut rectified voltage V _{Φ — R} . The load 716 with the electronic light source includes an interface circuit, such as a transformer, which provides power to the electronic light source.

FIG. 8 shows one embodiment of a zero-crossing and valid time detector 800 for detecting the trailing edge of the approximate zero-crossing values t _ZC (n) ₁ and t _ZC (n) ₂ of the phase-cut rectified voltage V _{Φ_R} In one embodiment of the dimmer high impedance state predictor 412 . The zero-crossing detector 800 includes a comparator 802 that compares the phase-cut rectified voltage V _{Φ_R} with a threshold value of the phase-cut rectified voltage V _{Φ_R} . The threshold value of the phase-cut rectified voltage _{VΦ_R} is, for example, in the range of 0 to 15V. When the comparator 802 detects that the phase-cut rectified voltage _{VΦ_R} has transitioned to be greater than the phase-cut rectified voltage _{VΦ_R} threshold, the ZC_DETECT output signal of the comparator 802 indicates a transition from logic 1 to logic 0. This transition indicates the detection of the first zero crossing t _ZC (n) ₁ . Next, the timer 804 starts counting at a frequency greater than the frequency of the phase-cut rectified voltage V _{Φ_R} . For example, in at least one embodiment, the timer 804 counts at a frequency above 10 kHz. When the comparator 802 detects that the phase-cut rectified voltage V _{Φ_R} is less than the phase-cut rectified voltage V _{Φ_R} threshold, the ZC_DETECT output signal of the comparator 802 indicates a transition from logic 0 to logic 1. A transition of the ZC_DETECT output signal from logic 0 to logic 1 indicates detection of the second zero crossing t _ZC (n) ₂ . Next, a timer 804 indicates the time between the detection of two zero crossings, which is an approximate actual effective time T _A (n).

FIG. 9 illustrates a current control module 900 that represents one implementation of the current control module 704 . The current control module 900 includes a controllable current source 902 . Current source 902 includes FETs 904 and 906 configured as a current mirror. Referring to FIGS. 7 and 9 , in at least one embodiment, the controller 908 modulates the control signal CS ₁ for controlling the current through the switch 707 to control power factor correction and regulate the link voltage V _LINK of the switching power converter 706 , The trailing accelerator current value i _{R_ACCEL} is generated, a low impedance state of switching power converter 7066 is generated, and excess power is dissipated, as previously described.

Current source 902 provides a reference current i _REF through FET 906 . In at least one embodiment, the control signal CS ₁ turns on the boost switch 707 . The size of FET 904 is scaled to the size of FET 906 by scaling factor Z. The value of the scaling factor Z is positive and is a design choice. The value of the scaling factor Z is multiplied by the value of the reference current i _REF to set the trailing edge accelerator current value i _{R_ACCEL} . Therefore, when the trailing edge dimmer high impedance state predictor 412 predicts that the high impedance state of the dimmer occurs t _HR (n), the controller 908 makes the controllable current source 902 transmit the trailing edge accelerator current value i _{R_ACCEL} to switching power converter 706 .

Accordingly, the electronic system includes a controller, and the controller provides compatibility between the electronic light source and the trailing edge dimmer. In at least one embodiment, the controller can predict the estimated occurrence of the trailing edge of the phase-cut AC voltage and can accelerate the transition of the phase-cut AC voltage from the trailing edge to a predetermined voltage threshold.

Although the embodiments have been described in detail, it should be understood that various changes, substitutions and alterations could be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (40)

1. A device comprising: a controller for providing compatibility between lamps and trailing edge dimmers, wherein the controller is capable of: predicting an estimated occurrence of a high impedance state of the trailing edge dimmer, wherein the high impedance state occurs when the trailing edge dimmer begins phase cutting an alternating current (AC) voltage signal; Prediction occurs based on an estimated high impedance state of the trailing edge dimmer, operating in a high current mode; and Operating in a low impedance mode after the AC voltage signal reaches a low voltage threshold. 2. The apparatus of claim 1, wherein the controller is further operable in a low impedance mode until a next approximate zero crossing of the AC voltage signal after phase cutting of the AC voltage signal. 3. The apparatus of claim 1, wherein the controller is capable of operating in a high current mode before the trailing edge dimmer begins phase cutting an alternating current (AC) voltage signal. 4. The apparatus of claim 3, wherein the controller is capable of operating in a high current mode within 0.1 ms before the trailing edge dimmer begins phase cutting an alternating current (AC) voltage signal. 5. The apparatus of claim 1, wherein the controller is capable of operating in a high current mode until an estimated prediction of a high impedance state of the trailing edge dimmer occurs. 6. The apparatus of claim 1 , wherein the controller is capable of predicting the current period of the AC voltage signal based on the actual occurrence trend of the high impedance state in the N immediately preceding periods of the AC voltage signal The estimation of the high impedance state of the trailing edge dimmer occurs in , where N is an integer greater than or equal to 2. 7. The apparatus of claim 1, wherein the controller is further capable of predicting the high impedance state of the trailing edge dimmer based on the profile of the voltage signal in N previous cycles of the voltage signal occurring before the current cycle The estimation of takes place, where N is an integer greater than or equal to 1. 8. The apparatus of claim 7, wherein the profile is a profile of the current drawn by the lamp. 9. The apparatus of claim 7, wherein the profile is a voltage profile of the lamp. 10. The apparatus of claim 9, wherein the voltage profile is determined based on a change in voltage in the AC voltage signal over time. 11. The apparatus of claim 1, wherein the AC voltage signal is a rectified AC voltage derived from a phase cut AC input supply voltage. 12. The apparatus of claim 1, wherein the controller is capable of controlling the power converter, wherein the power converter is coupled between the trailing edge dimmer and one of the lamps included in the lamp. or between multiple electron light sources. 13. The device of claim 1, wherein the light comprises a member of the group consisting of: one or more light emitting diodes, one or more compact fluorescent lamps, and one or more light emitting diodes and one or more a compact fluorescent lamp. 14. A method of providing compatibility between a lamp and a trailing edge dimmer, the method comprising: predicting an estimated occurrence of a high impedance state of the trailing edge dimmer, wherein the high impedance state occurs when the trailing edge dimmer begins phase cutting an alternating current (AC) voltage signal; causing at least a controller of the power converter to operate in a high current mode based on an estimated prediction of the high impedance state of the trailing edge dimmer; and Operating the controller in a low impedance mode after the AC voltage signal reaches a low voltage threshold. 15. The method of claim 14, further comprising: The controller is caused to operate in a low impedance mode until a next approximate zero crossing of the AC voltage signal following a phase cut of the AC voltage signal. 16. The method of claim 14, further comprising: The controller is caused to operate in a high current mode before the trailing edge dimmer begins phase cutting an alternating current (AC) voltage signal. 17. The method of claim 16, further comprising: The controller is caused to operate in a high current mode within 0.1 ms before the trailing edge dimmer begins phase cutting an alternating current (AC) voltage signal. 18. The method of claim 14, further comprising: The controller is caused to operate in a high current mode until an estimated prediction of a high impedance state of the trailing edge dimmer occurs. 19. The method of claim 14, further comprising: Predicting an estimated occurrence of the high impedance state of the trailing edge dimmer in the current cycle of the AC voltage signal based on an actual occurrence trend of the high impedance state in N immediately preceding cycles of the AC voltage signal, where N is an integer greater than or equal to 2. 20. The method of claim 14, further comprising: An occurrence of a phase-cut trailing edge of the alternating current (AC) voltage signal is predicted based on a profile of the voltage signal in N previous cycles of the voltage signal occurring prior to the current cycle, where N is an integer greater than or equal to one. 21. The method of claim 20, wherein the profile is a profile of the current drawn by the lamp. 22. The method of claim 20, wherein the profile is a voltage profile of the lamp. 23. The method of claim 22, further comprising: The voltage profile is determined based on a change in voltage in the AC voltage signal over time. 24. The method of claim 14, wherein the AC voltage signal is a rectified AC voltage derived from a phase cut AC input supply voltage. 25. The method of claim 14, further comprising: The power converter is controlled, wherein the power converter is coupled between the trailing edge dimmer and one or more electronic light sources included in the lamp. 26. The method of claim 14, wherein the lamp comprises a member of the group consisting of: one or more light emitting diodes, one or more compact fluorescent lamps, and one or more light emitting diodes and one or more a compact fluorescent lamp. 27. A device comprising: Controller, capable of doing the following: predicting the estimated occurrence of a high impedance state of a trailing edge dimmer that occurs when the trailing edge dimmer begins phase cutting an alternating current (AC) voltage signal of a phase cut AC voltage; and Accelerating the transition of the AC voltage from the trailing edge to a predetermined voltage threshold. 28. The apparatus of claim 27, wherein the controller is further capable of: operating in a high current mode to accelerate the transition of the AC voltage from a trailing edge to a predetermined voltage threshold based on an estimated prediction of a high impedance state of the trailing edge dimmer; and Operating in a low impedance mode after the AC voltage signal reaches a low voltage threshold. 29. The apparatus of claim 27, wherein the controller is capable of predicting the current period of the AC voltage signal based on the actual occurrence trend of the high impedance state in the N immediately preceding periods of the AC voltage signal The estimation of the high impedance state of the trailing edge dimmer occurs in , where N is an integer greater than or equal to 2. 30. The apparatus of claim 27, wherein the controller is further capable of predicting the high voltage of the trailing edge dimmer based on a valid voltage period of the voltage signal in N previous cycles of the voltage signal occurring before the current cycle. Estimation of the impedance state occurs, where N is an integer greater than or equal to one. 31. The apparatus of claim 27, wherein the AC voltage signal is a rectified AC voltage derived from a phase cut AC input supply voltage. 32. The apparatus of claim 27, wherein the controller is capable of controlling a power converter, wherein the power converter is coupled between the trailing edge dimmer and one or more between electronic light sources. 33. The apparatus of claim 27, wherein the light comprises a member of the group consisting of: one or more light emitting diodes, one or more compact fluorescent lamps, and one or more light emitting diodes and one or more a compact fluorescent lamp. 34. A method comprising: predicting the estimated occurrence of a high impedance state of a trailing edge dimmer that occurs when the trailing edge dimmer begins phase cutting an alternating current (AC) voltage signal of a phase cut AC voltage; and Accelerating the transition of the AC voltage from the trailing edge to a predetermined voltage threshold. 35. The method of claim 34, further comprising: causing at least a controller of a power converter to operate in a high current mode to accelerate transition of the AC voltage from a trailing edge to a predetermined voltage threshold based on an estimated predictive occurrence of a high impedance state of the trailing edge dimmer; and Operating the controller in a low impedance mode after the AC voltage signal reaches a low voltage threshold. 36. The method of claim 34, further comprising: Predicting an estimated occurrence of the high impedance state of the trailing edge dimmer in the current cycle of the AC voltage signal based on the actual occurrence trend of the high impedance state in N immediately preceding cycles of the AC voltage signal, where N is greater than or an integer equal to 2. 37. The method of claim 34, further comprising: An estimated occurrence of the high impedance state of the trailing edge dimmer is predicted based on a valid voltage period of the voltage signal in N previous cycles of the voltage signal occurring prior to the current cycle, where N is an integer greater than or equal to one. 38. The method of claim 34, wherein the AC voltage signal is a rectified AC voltage derived from a phase cut AC input supply voltage. 39. The method of claim 34, further comprising: The power converter is controlled, wherein the power converter is coupled between the trailing edge dimmer and one or more electronic light sources included in the lamp. 40. The method of claim 34, wherein the lamp comprises a member of the group consisting of: one or more light emitting diodes, one or more compact fluorescent lamps, and one or more light emitting diodes and one or more a compact fluorescent lamp.

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